Carburetor output control device

ABSTRACT

A device for optimizing the air/fuel ratio of a combustible mixture produced in a carburetter when atmospheric pressure and temperature deviate from given levels. When a bellows extends in response to the deviation from the given levels, atomospheric air is supplied downstream of a carburetter throttle valve through a diaphragm valve assembly responsive to the extension of the bellows during idling or light-load operation of an engine, while air is supplied to a main mixture supply passage through another diaphragm valve assembly responsive to the operation of the first-mentioned assembly during full-load operation.

United States Patent Masaki [451 May 14, 1974 CARBURETOR OUTPUT CONTROLDEVICE Inventor: Kenji Masaki, Yokohama, Japan Nissan Motor CompanyLimited, Yokohama City, Japan Filed: Jan. 26, 1973 Appl. No.: 326,993

Assignee:

Foreign Application Priority Data Feb. 1, 1972 Japan 47-11972 US. Cl261/39 A Int. Cl. F02m l/10, F02m l/l4 Field of Search 261/39 A, 121 BReferences Cited UNITED STATES PATENTS 2/1954 Sager 261/39 A PrimaryExaminer-Francis S. Husar Attorney, Agent, or FirmRobert E. Burns;Emmanuel J. Lobato [57] ABSTRACT A device for optimizing the air/fuelratio of a combustible mixture produced in a carburetter whenatmospheric pressure and temperature deviate from given levels. When abellows extends in response to the deviation from the given levels,atomospheric air is supplied downstream of a carburetter throttle valvethrough a diaphragm valve assembly responsive to the extension of thebellows during idling or light-load operation of an engine, while air issupplied to a main mixture supply passage through another diaphragmvalve assembly responsive to the operation of the firstmentionedassembly during full-load operation.

10 Claims, 1 Drawing Figure 1 CARBURETOR OUTPUT CONTROL DEVICE Thisinvention relates, in general, to a carburetter for use with anautomotive internal combustion engine and more particularly to a deviceconnected to the carburetter for optimizing the air/fuel ratio of acombustible mixture in accordance with climatic conditions such asatmospheric pressure and temperature.

It has been commonly observed that the operational characteristics of acarburetter, particularly the working strength of the combustiblemixture are affected by changes in atmospheric pressure and temperature.When a vehicle is driven in summer or at high altitudes, air/fuelmixture is found to be richer than in other, more normal circumstances.This effect is due to the fact that the density of air diminishes withthe rise of its temperature and the drop of its pressure, and thereforerelatively small weight of air is drawn into the engine. As a result, aportion of mixture supplied to a combustion cylinder will remainunburned, since the quantity of air does not suffice for a completecombustion in the cylinder. The unburned contents thus contained in theexhaust gases are passed through the exhaust system of the engine to theatmosphere, thus causing serious air pollution. Moreover, in case of theengine being provided with an exhaust gas cleaning device such as athermal reactor or a catalytic converter or the like, the unburnedcontents may be deposited onto parts of the cleaning device. Whilst suchdeposition alone will adversely affect the performance of the device, anuntimely and incomplete burning of the deposited unburned contents mayhappen, thus almost entirely eliminating the effects of such cleaningdevice.

A primary object of the present invention is therefore to provide a newand improved device which can obviate the drawbacks accompanied byconventional carburetters as mentioned.

Another object is to provide a device for correcting and optimizing theair/fuel ratio of a combustible mixture for the climatic condition inwhich the carburetter is used at any one time.

Still another object is to supply an unnecessarily enriched combustiblemixture with fresh air when the atmospheric temperature is high and theatmospheric pressure is low.

A further object is to provide optimization of the air/fuel ratio of themixture under all driving conditions of a vehicle including idling andacceleration.

A still further object is to raise the engine operational performanceparticularly when a vehicle is running at a high altitude.

Other objects and advantages will appear from the following descriptionof an embodiment of the present invention when taken together with theaccompanying drawing, wherein A single FIGURE is a schematic sectionalview of a carburetter equipped with a device according to the presentinvention.

Reference is now made to the single FIGURE, wherein a carburettergenerally designated by numeral is, as usual, constituted by aninduction passage 11 leading to an intake manifold (not shown), athrottle valve 12 located intermediate the induction passage 11, a floatchamber 13 with a float 14, a main mixture circuit l5 and an idling andslow-running mixture circuit 16, the former being connected between thefloat chamber 13 and the induction passage 11 and the latter branchingoff from the circuit 15. The induction passage 11 is formed with aventuri or choke tube 17 upstream of the throttle valve 12. The mainmixture circuit 15 comprises a main fuel jet 18 adjacent the floatchamber 13, a main air/fuel mixer 19 which encloses therein an air bleedtube 20, and a main nozzle 21 opening into the venturi portion 17 of theinduction passage. The idle and slow running mixture circuit 16 isbranched off from the main mixture circuit 15 posterior to the main jet18 and leads to a slow running port 22 and further to an idling port 23,the former of which opens into the induction passage 11 adjacent theperiphery of the closed throttle valve, and the latter downstream of thethrottle valve. The effective area of this idling port 23 is preferablyadjustable by a needle valve 24. The idling and slow-running mixturecircuit 16 further comprises a plurality of air bleed restrictors asindicated at 24 and 25.

Whilst the construction heretofore described is that of the averagestate of the art, the device according to the invention and itsoperation will be described in detail below in connection with the aboveand known carburetter.

Represented by numeral is a device for compensating for the mixtureenrichment above a given level of atmospheric temperature and belowanother given level of atmospheric pressure. The device 30 substantiallyconsists of a combined bellows and diaphragm valve assembly 31 andanother diaphragm valve assembly 32. The valve assemblies are disposedaxially and spacedly opposite to each other forming a control chamber 33between a valve seat 46 of the valve assembly 31 and a diaphragm 49 ofthe valve assembly 32. A housing 34 forms a chamber accommodating thefirst assembly 31 and divided by a diaphragm 35 into an upper chamber 36and a lower chamber 37. The upper chamber 36 accommodates therein abellows 38 which is filled with an inert gas such as nitrogen. The topof the bellows 38 is connected to a pressure regulator valve 39 whichis, in turn, mounted on the upper wall of the housing 34 for maintainingthe pressure in the inert gas at a constant level. The bottom of thebellows 38 is supported on and secured to the diaphragm 35. Penetratingthrough the side wall of the upper chamber 36, a plurality of air vents40 are formed, through which atmospheric air circulates around thebellows and influences the inert gas filling the bellows 38. Thebellows, thus sensing a change in temperature and pressure, will extendand when they reach given levels the bellows will move the diaphragm 35.The assembly 31 further includes a stem 41 secured to and extending Ifrom the diaphragm 35 through the lower chamber 37.

The diaphragm 35 is biased upwardly in the drawing by a spiral spring 42mounted in the lower chamber 37. The lower chamber 37 is connectedthrough a conduit 43 to an air cleaner (not shown) of the engine. Fromthe center portion of the lower chamber 37, a tubular small housing 44defining the control chamber 33 extends toward the opposite side of the'housing 34 or downwardly in the drawing. An annular valve seat 46 isprovided on the inner circumferential w'allof the tubular housing toform the valve 45 which separates the control chamber 33 from the spacecontinuing to the lower chamber 37. The valve stem 41 has at its leadingend a valve head 47 which is tapered upwardly in the I drawing. Thevalve 45 controls the flow therethrough by the tapered valve head 47 inaccordance with the degree of displacement of the diaphragm 35. Withthis construction, air is fed through the air cleaner into the chamber33 through the lower chamber 37 in varying amounts which depend on thechanges in the open area of the valve 45.

, A housing 48 accommodating the other diaphragm valve assembly 32 issimilarly formed as, but smaller in diameter than the housing 34, andmade integral with the tubular housing 44. The inner space of thishousing 48 is also divided by a diaphragm 49 into an upper chamber 50continuing to the control chamber 33 and another control chamber 51.Just as in the first assembly 31, a spiral spring 52 is mounted in theupper chamber 50 for slightly biasing the diaphragm 49 downwardly.Through the control chamber 51, a valve stem 53 extends from thediaphragm 49 and has an upwardly tapered valve head 54 at its leadingend. The control chamber 51 is communicable with air through a valve 55formed by an annular valve seat 56 and the valve head 54. The movementof the diaphragm 49, in this assembly, occurs in response to the airpressure established in the control chamber 33 and hence only indirectlyresponds to the extension of the bellows 38.

The control chambers 33 and 51 respectively communicate with theinduction passage 11 downstream of the throttle valve 12 through aconduit 60 and with the main air/fuel mixer 19 through a conduit 61.Thus, air present in these chambers is admitted into conduits 60 and 61in dependence on various driving conditions, as will be hereinafterdiscussed. The conduits 60 and 61 are respectively provided withrestrictors 62 and 63 for throttling purposes.

lnoperation, the valve 45 is kept closed by the valve head 47 of thestem 41 under normal temperature and pressure, the carburetter thenfunctioning as usual. Neither does the assembly 32 operate, sincedepression in the induction passage 11 is transmitted to the controlchamber 33.

As the temperature rises or the pressure falls, or both occurconcurrently, the gas filling the bellows 38 tends to expand, thusextending the bellows toward the lower chamber 37. The diaphragm 35 isthen moved downward to open the valve 45. As a result, air flowingthrough, the conduit 43 is allowed into the control chamber 33 throughthe lower chamber37 and the valve 45. if the throttle valve takes anidlingposition indicated at a solid line in the drawing or a slightlymore opened position, a pressure difference is established between theinduction passage downstream of the throttle valve and the controlchamber 33 which is supplied with air in the above described manner. Airin the control chamber 33 is therefore sucked into the induction passagedownstream of the throttle valve through the conduit 60.

If, however, the throttle valve is fully opened to the dotted position,the suction in the induction passage downstream of the throttle valveis, if any, not enough to draw air in the control chamber 33, while atthe same time suction develops in the venturi portion 17. Supply of airto the induction passage downstream of the throttle valve thereforestops under such heavyload operation of the engine. Since, in themeantime, the air pressure which is higher than the pressure in theventuri portion 17 remains in the control chamber 33,

, 6 the diaphragm 49 of the second assembly 32 18 also moved downwardmostly by the pressure in the chamber 33 and partly by the biasing forceof the spring 52.

Thus the valve 55 is open to allow air therethrough into the controlchamber 51. As the air pressure in the chamber 33 approximates theatmospheric pressure, the opening degree of the valve 55 increases andthe correspondingly increasing amount of air feeds the chamber 51. Thesuction established in the venturi portion 17 now starts to draw airpresent in the chamber 51 through the conduit 61 into the lower portionof the main mixer 19. Since only a small amount of air feeding the mainmixer is sufficient for the purpose of weakening the mixture, theconduit 61 leading to the main mixer 19 may be of small diameter. Thequantities of air flowing through the conduits and 61 are respectivelycontrolled by the restrictors 62 and 63.

Throughout the description above, it will be noted that the presentinvention provides an optimum mixture strength under any climaticcondition. It should be also appreciated that the device of the presentinvention operates independently for idling or light-load operation andfor full load operation.

Moreover, certain kind of troubles in the engine performance are solvedby the device of the present invention. The troubles are, e.g., suchthat the engine speed at idling decreases and finally the engine tendsto stall when atmospheric pressure is low at high altitudes. This effectis again caused by the enrichment effect of the mixture, which can beweakened through supplying the induction passage downstream of thethrottle valve with air in the manner described.

While 1 have shown and described a specific embodiment of my invention,it will be readily understood that many changes and modifications instructure and operation can be made without departing from the scope ofthe invention as defined only by the appended claims.

What is claimed is:

1. in a carburetter for an internal combustion engine including aninduction passage, a throttle valve dividing said induction passage intoan upstream part and a downstream part, and a main mixture supplypassage opening into said upstream part of the induction passage,

a carburetter control device comprising:

a first control chamber communicating with the downstream part of theinduction passage and being communicable with the atmosphere;

a second control chamber communicating with said main mixture supplypassage and communicable with atmosphere;

means operable in response to at least one of an atmospheric pressurebelow a given pressure level and an atmospheric temperature above agiven temperature level, for providing communication between said firstcontrol chamber and the atmosphere to introduce additional air into thedownstream part of the induction passage in an amount varying indegrees; and

air pressure responsive means operable in response to an air pressureprevailing in said first control chamber, for providing communicationbetween said second control chamber and the atmosphere to introduceadditional air into said main mixture supply passage in an amountvarying in degrees.

2. A device according to claim 1, further comprising a first air supplyconduit connected between said first control chamber and said downstreampart of the induction passage.

3. A device according to claim 2, wherein said first air supply conduitincludes a flow restrictor.

4. A device according to claim 1, further comprising a second air supplyconduit connected between said second control chamber and said mainmixture supply passage.

5. A device according to claim 4, wherein said second air supply conduitincludes a flow restrictor.

6. A device according to claim 1, wherein said firstmentioned meanscomprises a bellows filled with an inert gas to extend in response tosaid at least one ofthe atmospheric pressure and temperature, adiaphragm member secured to said bellows and movable therewith, and avalve member connected to said diaphragm member and movable therewith,said valve member having a tapered valve head to vary the degree ofcommunication between said first control chamber and the atmosphere.

7. A device according to claim 6, wherein said inert gas is nitrogen.

8. A device according to claim 6, wherein said firstmentioned meansfurther comprises a spring for biasing said diaphragm member to causesaid valve member to interrupt communication between said first controlchamber and the atmosphere.

9. A device according to claim 1, wherein said air pressure responsivemeans comprises a diaphragm member yieldably disposed between said firstand second control chambers and a valve member connected to saiddiaphragm member and movable therewith, said valve member having atapered valve head to vary the degree of communication between saidsecond control chamber and the atmosphere.

10. A device according to claim 9, wherein said air pressure responsivemeans further comprises a spring disposed in said first control chamberfor biasing said diaphragm member in a direction to cause said valvemember to establish communication between said second control chamberand the atmosphere.

1. In a carburetter for an internal combustion engine including aninduction passage, a throttle valve dividing said induction passage intoan upstream part and a downstream part, and a main mixture supplypassage opening into said upstream part of the induction passage, acarburetter control device comprising: a first control chambercommunicating with the downstream part of the induction passage andbeing communicable with the atmosphere; a second control chambercommunicating with said main mixture supply passage and communicablewith atmosphere; means operable in response to at least one of anatmospheric pressure below a given pressure level and an atmospherictemperature above a given temperature level, for providing communicationbetween said first control chamber and the atmosphere to introduceadditional air into the downstream part of the induction passage in anamount varying in degrees; and air pressure responsive means operable inresponse to an air pressure prevailing in said first control chamber,for providing communication between said second control chamber and theatmosphere to introduce additional air into said main mixture supplypassage in an amount varying in degrees.
 2. A device according to claim1, further comprising a first air supply conduit connected between saidfirst control chamber and said downstream part of the induction passage.3. A device according to claim 2, wherein said first air supply conduitincludes a flow restrictor.
 4. A device according to claim 1, furthercomprising a second air supply conduit connected between said secondcontrol chamber and said main mixture supply passage.
 5. A deviceaccording to claim 4, wherein said second air supply conduit includes aflow restrictor.
 6. A device according to claim 1, wherein saidfirst-mentioned means comprises a bellows filled with an inert gas toextend in response to said at least one of the atmospheric pressure andtemperature, a diaphragm member secured to said bellows and movabletherewith, and a valve member connected to said diaphragm member andmovable therewith, said valve member having a tapered valve head to varythe degree of communication between said first control chamber and theatmosphere.
 7. A device according to claim 6, wherein said inert gas isnitrogen.
 8. A device according to claim 6, wherein said first-mentionedmeans further comprises a spring for biasing said diaphragm member tocause said valve member to interrupt communication between said firstcontrol chamber and the atmosphere.
 9. A device according to claim 1,wherein said air pressure responsive means comprises a diaphragm memberyieldably disposed between said first and second control chambers and avalve member connected to said diaphragm member and movable therewith,said valve member having a tapered valve head To vary the degree ofcommunication between said second control chamber and the atmosphere.10. A device according to claim 9, wherein said air pressure responsivemeans further comprises a spring disposed in said first control chamberfor biasing said diaphragm member in a direction to cause said valvemember to establish communication between said second control chamberand the atmosphere.